Universidad Católica de la Santísima Concepción, Alonso de Ribera 2850, Casilla 297, Concepción, Chile; Centro de Investigación en Biodiversidad y Ambientes Sustentables (CIBAS), Alonso de Ribera 2850, Casilla 297, Concepción, Chile; Department of Geology and Environmental Science, University of Pittsburgh, Pittsburgh, PA 15260, USA.
Department of Geology and Environmental Science, University of Pittsburgh, Pittsburgh, PA 15260, USA.
Sci Total Environ. 2023 Oct 15;895:165065. doi: 10.1016/j.scitotenv.2023.165065. Epub 2023 Jun 22.
Southern South America is the only large landmass that extends through the core of the Southern Westerly Winds (SWW), controlling hydrological and ecosystem variability in the region. In fact, the vegetation along the west coast changes from Temperate and Valdivian Rain Forest to the North Patagonian Evergreen Forest (ca. 42°S) due to the latitudinal influence of the SWW. Climate is an important driver of organic matter accumulation in lakes, hence changes in vegetation would be recorded in lacustrine sedimentary archives. This study evaluated leaf waxes contained in lake surface sediments as indicators of climate change along the west coast of southern South America, providing a biogeochemical dataset for ongoing and future (paleo)climate and environmental research. The fatty acid and n-alkane sediment leaf wax datasets are compared with latitudinal, orographic, and climatic (Mean Annual air Temperature [MAT] & Precipitation [MAP]) trends extracted from a monthly gridded reanalysis product of the Climate Forecast System Reanalysis. Fatty acids are more abundant than n-alkanes, with high abundances characterizing the transition between seasonal and year-round precipitation along the coast (ca. 42°S). The abundance of both leaf wax groups increases with MAP, suggesting precipitation as the main control on sedimentary leaf wax delivery to the lake sediments in the study area. The Carbon Preference Index (CPI) of the two groups show opposite trends, but both highlight the climate transition at ca. 42°S, and have a linear relationship with MAP. The opposite significant trends between n-alkane CPI and fatty acid CPI with MAP are interpreted as higher n-alkane production at much higher precipitation because leaf wax fatty acids are the precursors of n-alkanes. Hence, past periods during which these leaf waxes show opposite trends in CPI might be interpreted as a precipitation change, especially if additional information such as pollen, diatoms, chironomids and stable isotopes is available.
南美洲南部是唯一一块贯穿西风核心带（SWW）的大型陆地，控制着该地区的水文和生态系统变化。事实上，由于 SWW 的纬度影响，西海岸的植被从温带和瓦尔迪维亚雨林变为北巴塔哥尼亚常绿森林（约 42°S）。气候是湖泊有机质积累的重要驱动因素，因此植被变化将被记录在湖泊沉积档案中。本研究评估了湖泊表层沉积物中所含的叶蜡作为南美南部西海岸气候变化的指标，为正在进行的和未来的（古）气候和环境研究提供了一个生物地球化学数据集。脂肪酸和正烷烃沉积物叶蜡数据集与纬度、地形和气候（年均空气温度 [MAT] 和降水量 [MAP]）趋势进行了比较，这些趋势是从气候预测系统再分析的每月网格化再分析产品中提取的。脂肪酸比正烷烃更丰富，高丰度特征是沿海岸季节性和全年降水之间的过渡（约 42°S）。两组叶蜡的丰度都随降水量增加而增加，表明降水是控制研究区湖泊沉积物中沉积叶蜡输送的主要因素。两组叶蜡的碳偏好指数（CPI）表现出相反的趋势，但都突出了约 42°S 的气候转变，与降水量呈线性关系。正烷烃 CPI 和脂肪酸 CPI 与降水量呈相反显著趋势，这是因为在更高的降水量下，正烷烃的生成量更高，而叶蜡脂肪酸是正烷烃的前体。因此，如果有花粉、硅藻、摇蚊和稳定同位素等其他信息可用，过去这些叶蜡 CPI 呈相反趋势的时期可能被解释为降水变化。
